Not Applicable
The present invention relates generally to optical switches and in particular to a wavelength cross-connect.
Optical switches are commonly used in communications systems for transmitting voice, video and data signals. An optical cross-connect is an optical switch that includes multiple input and/or output ports and has the ability to connect, for purposes of signal transfer, any input port/output port combination, and preferably, for Nxc3x97M switching applications, to allow for multiple connections at one time. A wavelength cross-connect is a cross-connect that allows individual channels of a wavelength multiplexed optical signal to be switched or routed independently from the others.
Generally, optical signals are transmitted and/or received at each port of a switch via an end of an optical waveguide. The waveguide ends of the input and output ports are optically coupled via a switch core. In this regard, for example, the input and output waveguide ends can be physically located on opposite sides of a switch core for direct or folded optical pathway communication therebetween, in side-by-side matrices on the same physical side of a switch core facing a mirror, or they can be interspersed in a single matrix arrangement facing a mirror.
Establishing a connection between a given input port and a given output port, involves configuring an optical pathway across the switch core between the input ports and the output ports. One way to configure the optical pathway is by moving or bending optical fibers using, for example, piezoelectric benders. Another way of configuring the optical path between an input port and an output port involves the use of one or more moveable deflectors interposed between the input and output ports. In this case, the waveguide ends remain stationary and the deflectors are used for switching. For example, moveable mirrors can allow for one-dimensional or two-dimensional targeting to optically connect any of the input port fibers to any of the output port fibers and vice versa. For example, U.S. Pat. No. 5,914,801, entitled MICROELECTROMECHANICAL DEVICES INCLUDING ROTATING PLATES AND RELATED METHODS, which issued to Dhuler et al on Jun. 22, 1999; U.S. Pat. No. 6,087,747, entitled MICROELECTROMECHANICAL BEAM FOR ALLOWING A PLATE TO ROTATE IN RELATION TO A FRAME IN A MICROELECTROMECHANICAL DEVICE, which issued to Dhuler et al on Jul. 11, 2000; and U.S. Pat. No. 6,134,042, entitled REFLECTIVE MEMS ACTUATOR WITH A LASER, which issued to Dhuler et al on Oct. 17, 2000, disclose micro-electromechanical mirrors that can be controllably moved in two dimensions to effect optical switching.
In wavelength cross-connects, it is generally necessary to demultiplex the optical signal before independent wavelengths are switched and remultiplex after the wavelength signals are switched. For example, both U.S. Pat. No. 6,097,859 entitled MULTI-WAVELENGTH CROSS-CONNECT OPTICAL SWITCH, issued to Solgard et al on Aug. 1, 2000, and U.S. Pat. Appl. No. 200020033976 entitled METHOD AND DEVICE FOR SWITCHING WAVELENGTH DIVISION MULTIPLEXED OPTICAL SIGNALS USING GRATINGS to Holmes, published on Mar. 21, 2002, disclose a switch wherein light is demultiplexed/multiplexed via a wavelength dispersive grating.
The instant invention relates to a wavelength cross-connect that utilizes a dispersive system, such as a dispersive grating, for demultiplexing and multiplexing optical signals and a switch core based on independently controllable deflectors. Advantageously, the switch core uses cylindrical optics including an angle-to-offset (ATO) element disposed between the deflectors to provide for a re-imaging, and hence a low loss.
In accordance with the invention there is provided a wavelength cross-connect comprising: an input port for launching an optical beam into the wavelength cross-connect; dispersive means for spatially separating the optical beam into individual wavelength channels; beam deflecting means optically coupled to the dispersive means for selectively deflecting each of the individual wavelength channels in a predetermined manner; a ATO element for providing angle to offset transformation for each of the deflected wavelength channels; relay means for relaying light corresponding to each of the individual wavelength channels to and from the ATO element; and a plurality of output ports, wherein said wavelength cross-connect is configured for independently switching at least one wavelength channel from the input port to one of the plurality of output ports.
In accordance with the invention there is provided a wavelength cross-connect comprising: an input port for launching a beam of light into the wavelength cross-connect; a first dispersive element for dispersing the beam of light into a plurality of sub-beams of light; a switch core for routing each sub-beam along a respective predetermined optical path therein; a second dispersive element for recombining the plurality of sub-beams routed by the switch core to produce a plurality of output beams of light, each output beam having a composition dependent on the respective predetermined optical paths; a plurality of output ports, each output port for respectively receiving one of the plurality of output beams; and beam redirecting means for providing an optical pathway between the input port, the first dispersive element, the switch core, the second dispersive element, and the plurality of output ports, wherein the switch core includes: first and second opposed optical arrays, each optical array including a plurality of independently operable beam deflectors; an ATO element having optical power disposed between the first and second opposed optical arrays for providing an angle-to-offset transformation for light transmitted between the first and second optical arrays; and relay means for redirecting light transmitted between the first optical array and the second optical array via the ATO element.
In accordance with the invention there is provided a wavelength cross-connect comprising: N linearly aligned input ports; a first diffraction grating for dispersing an input beam of light launched from one of the N input ports into M wavelength channel signals, said first diffraction grating having grating lines substantially parallel to the direction in which the plurality of input ports are aligned; a first deflector array including Nxc3x97M independently controlled elements, said first deflector array disposed such that each channel signal transmitted from the first diffraction grating is passed to a separate element on the first deflector array; a second deflector array including Nxc3x97M independently controlled elements, said second deflector array opposing the first deflector array; a cylindrical ATO lens optically disposed between the first and second deflector arrays, said ATO lens disposed for providing angle to offset transformations in a direction parallel to the grating lines; first and second cylindrical relay lenses disposed for providing optical power in a plane perpendicular to the grating lines, said first relay lens optically disposed between the first deflector array and the ATO lens, said second relay lens optically disposed between the second deflector array and the ATO lens; a second diffraction grating for combining channel signals transmitted from the second deflector array into a plurality of output beams of light; and N linearly aligned output ports for receiving the plurality of output beams of light.
In accordance with the invention there is provided a wavelength cross-connect comprising: a first optical array including an array of independently controlled deflector elements; a second optical array including an array of independently controlled deflector elements, said second optical array opposing said first optical array; a cylindrical ATO lens optically disposed between said first and second optical arrays, said ATO lens disposed for transforming an angle induced by the first optical array into an offset at the second optical array; and first and second cylindrical relay lenses disposed for providing optical power in a plane perpendicular the offset, said first relay lens optically disposed between the first optical array and the ATO lens, said second relay lens optically disposed between the second optical array and the ATO lens.